So here's the case. Two young kids disappear in small town Arkansas in the heart of the Ozarks. The lead detective is a man named Wayne Hays, played by Mahershala Ali - a man haunted by the evil he uncovers.

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MAHERSHALA ALI: (As Wayne) I never stop coming up with theories about that case.

CARMEN EJOGO: (As Amelia) Whatever you think you did or didn't do, you don't deserve to suffer.

ALI: (As Wayne) This case is all I can think of. I want to know the whole story.

MARTIN: HBO's "True Detective" is back with a dark and sinister investigation set in 1980. And in this season, uncovering the truth behind the kidnapping involves a woman - a schoolteacher named Amelia Reardon, played by Carmen Ejogo.

EJOGO: She becomes embroiled in the case because the children that go missing are children that she taught. And so often, the teacher is perhaps the person that they are closest to, even more so than their parents. And that's very much the scenario with our story.

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ALI: (As Wayne) Anything you can tell me about Will?

EJOGO: (As Amelia) He has a sensitivity. You always worry a bit about the sensitive ones. I don't think he got noticed much.

MARTIN: The investigation draws Detective Hays to Amelia. Carmen Ejogo says the two are bound together by the case.

EJOGO: In many ways, they should never have come together. They have nothing in common. But fate brings us together. And they're also very other, being part of this community that, really, doesn't quite know what to do with them. You know, Wayne is a detective. He's a trailblazer. He's the first detective, the first cop in the force to reach that position.

MARTIN: The first black cop.

EJOGO: That's right. And I am a sort of biracial sort of worldly teacher who has ambitions that are above my station if you ask certain people, you know, within the community. So despite all of their inequities, all the things that don't really match up or make sense on paper, there is something that is inevitable about the relationship.

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ALI: (As Wayne) You from this area?

EJOGO: (As Amelia) Fayetteville.

ALI: (As Wayne) How is it here?

EJOGO: (As Amelia) It's good, really, for what it is. I hear something now and then.

ALI: (As Wayne) What you hear now and then?

EJOGO: (As Amelia) You know, a word in the hallway or something. They're careful around me.

MARTIN: Tell me about your experience in Fayetteville. This is the setting for this story. You actually filmed it there, right?

EJOGO: We did, yeah. I'd never been there before, and I - so I had no idea what to expect. And as I found myself in Fayetteville, I realized that it was a college town. On the surface, it felt very liberal and progressive in many ways. But it was interesting because as I spent more and more time there, I could feel that there's clearly a racial history to that place that is not necessarily blatantly (laughter) on display. It almost felt quite British at times, where, you know, it felt very pleasant but that I could just feel under the surface that there is some other kind of relationship between black and white in that town that might be a lot more complicated.

MARTIN: I want to play a clip, which kind of gets to what you're talking about in terms of how the story deals with race. And this is of Detective Wayne Hays questioning a white woman about the man they suspect may be behind the kidnapping, so let's listen.

EJOGO: (Laughter) I knew you were going to stop right there (laughter).

MARTIN: Such an amazing clip.

EJOGO: Yeah.

MARTIN: It says so much.

EJOGO: Yeah. She's completely oblivious to the irony of the fact that she's talking like this to a black man, you know? And that's the sort of stuff that, I think, is most interesting to explore because it really is the subtleties of racism that creep up on these characters.

MARTIN: Mahershala Ali has talked openly about the fact that he was originally considered for the secondary detective character. He was not considered for the lead. It was supposed to go to a white actor. In fact, he told us as much in an interview last year that he had to advocate for himself. He had to suggest to them that he play the lead. Asking you, I suppose, to engage in some revisionist history, but if Mahershala Ali hadn't been cast as Wayne Hays, where would that have left you?

EJOGO: It probably would have left me out of a job, frankly (laughter), which is, you know, very often the case with these sorts of storylines is the most interesting female role is going to play opposite the male lead. And that's usually white, you know? But thankfully, things have really taken a turn over the past several years. And you have a sort of wonderful convergence now of actors continually advocating for their value as leads and that - the convergence with an industry that now recognizes that there is value in that too is kind of the sweet spot that we seem to have arrived at, which is why, I think, Mahershala - you know, aside from his awesome, clear talent, I think that's probably why he won his case.

MARTIN: You have played the role of a wife a few times now, most famously as Coretta Scott King in two different films. And these are, obviously, very different roles. But whether it's the wife of a civil rights icon or the wife of a high-profile detective, I wonder if you have learned something about the power that these women have, what that particular role as spouse, as wife, carries with it.

EJOGO: Yeah. I mean, it's funny. I almost didn't do this job for that very reason.

MARTIN: Really?

EJOGO: Yeah, because that always suggests that it's going to be you're just supporting the man in the show.

MARTIN: Right.

EJOGO: I was only shown the first few episodes. And I really didn't fully appreciate or wasn't able to fully appreciate just how important and pivotal this role really is. Thank goodness I made the decision to come on board because I really had the opportunity and the space to play somebody who is affecting a man and being self-affecting in a way that, I think, an audience can really see that growth and what that can look like in a woman. And it also explores what it looks like in the man in the relationship.

He becomes quite threatened by her growth. And the fact, though, that they then, perhaps, find their way through that is what made it worth playing another wife (laughter). And as a result, I think I might be one of the most complex characters in the show, so I'm really glad I went for it in the end.

MARTIN: Carmen Ejogo plays Amelia Reardon in the new season of HBO's "True Detective." Carmen, thanks so much for talking with me.